1. Field of the Invention
The present invention relates generally to imaging systems such as electrophotographic (EPG) printers and copiers. More particularly, the present invention relates to imaging systems that are configurable in terms of printing routines, such a single-pass imaging, two-pass imaging, and so on. The imaging systems of the present invention utilize a removable module that allows a user to upgrade the imaging system with a module of higher quality (i.e., greater speed, better resolution, and so on) and then to reconfigure the printing routine based on the number of exposing units included in the replacement module.
2. Description of Related Art
Once exclusive to large companies, photocopiers and laser printers have become ubiquitous in homes and in businesses large and small. Photocopiers and laser printers operate according to electrophotographic (EPG) printing technology. Advances in EPG technology has enabled manufacturers to meet the demand for high-quality laser printing and copying of the small office/home office (SOHO) market. For example, many manufacturers design and market moderately priced xe2x80x9cpersonalxe2x80x9d photocopiers that operate at moderate speeds of about eight pages to ten pages per minute (ppm). Complementing affordable photocopiers, there are a number of moderately priced laser printers on the market that also operate at these moderate speeds.
While color inkjet printers are commonplace, the same is not so for color EPG systems. Color photocopiers and laser printers are large and expensive. With respect to color laser printers, the footprint of such systems (i.e., the area of a surface occupied by a printer), as well as the vertical clearance, is nearly twice as large as that of a monochrome (i.e., black-only printing) model. In addition, the price of color laser printers is nearly twice as high as that of monochrome models with comparable printing speeds.
Although larger and more expensive, color EPG printers have a clear advantage over inkjet printers in workgroup environments where a printer is connected to several users. Affordable color inkjet printers print at very slow speeds, such as 2 ppm or 3 ppm for high-resolution images, which is unacceptable in workgroups. Only the most expensive color inkjet printers are able to print at moderate speeds of 10 ppm, which is still too slow for effectively functioning in a workgroup environment. Accordingly, if it is desired to connect a color printer in a workgroup, then the printer needs to be a color laser printer.
Large size and high price of laser printers result from complicated EPG printing arrangements and processes. Standard EPG printing processes consist of six basic steps: charging, exposing, developing, transferring, fusing, and cleaning. For a general discussion of six-step printing processes, see, for example, pages 2110 to 2116 by Robert C. Durbeck in The Electrical Engineering Handbook, 2nd ed. (CRC Press, Boca Raton, Fla., 1997), the entire disclosure of which is incorporated herein by reference. For a more detailed discussion of six-step printing processes, see, for example, pages 26 to 49, of Electropholography and Development Physics, 2nd ed., by Lawrence B. Schein (Laplacian Press, Morgan Hill, Calif., 1996), the entire disclosure of which is also incorporated herein by reference.
Standard color printing involves the use of four differently colored toners: yellow, magenta, cyan, and black. Conventional color laser printers include a printing station with components for carrying out the charging, exposing, and developing steps. To print in color, the six-step EPG process is carried out for each color toner, that is, four times, which results in slow printing speeds. In order to operate at higher speeds, conventional EPG color printers are provided with additional printing stations, with each printing station dedicated to one of the four colors. While such an arrangement increases speed, the additional printing stations. accordingly increase cost, size, and complexity.
In view of the foregoing, there is a tradeoff in the art of color laser printing between speed and cost. For example, if a user wants to print at high speeds, then an expensive printer needs to be purchased. If a user is on a budget, then a slower and more affordable printer needs to be purchased, and if such a user foresees increased printing needs in the future, then a higher quality printer will need to be purchased in the future. Accordingly, there remains a need in the art for imaging systems that are able to print at moderate speeds at an affordable price and that are upgradeable to be able to print at higher speeds.
In preferred embodiments, the present invention provides upgradeable imaging systems and methods for upgrading imaging systems. The imaging systems of the invention enable users to purchase a moderately priced imaging system such as a color laser printer or a color photocopier that operates at moderate speeds, e.g., 8 pages per minute (ppm), and then to reconfigure the imaging system at a later time to operate at higher speeds, e.g., 16 ppm or 18 ppm.
According to one aspect of the invention, a preferred embodiment of an imaging system includes a plurality of imaging stations for forming an image on a sheet and a removable module including a photoreceptive substrate. An interior space is defined within the photoreceptive substrate in which at least one exposing unit is disposed. The imaging system also includes support structure for receiving the removable module, with the removable module being configured to be engageable with the support structure and, when engaged, to be disposed in an operative relationship with the imaging stations. In addition, the imaging control circuitry includes imaging control circuitry for configuring the imaging stations to operate according to a printing routine based on the number of exposing units.
The imaging systems of the present invention have a number of advantages, one of which is that the speed and, accordingly, the price of the imaging system may be changed by only changing the number of exposing units disposed on the removable module. An example of this advantage will be provided in the context of color electrophotographic (EPG) imaging where four imaging stations are provided, one for each of the four color toners: yellow, magenta, cyan, and black. In this context, the imaging system may be manufactured with a removable module with only two exposing units, which may include light-emitting diode (LED) print heads (LPHs). The imaging system may then be configured to operating according to a two-pass imaging routine. The speed of such a two-pass imaging system is moderate. As LPHs are expensive, the price of such an imaging system is moderate as there are only two exposing units.
However, a user may desire to upgrade the imaging system by acquiring a removable module with four exposing units. The two-unit module may be removed and then replaced with the four-unit module. The imaging system may then be configured to operate according to a single-pass imaging routine, which is essentially twice as fast as a two-pass system. This upgradeable feature of the present invention allows a user on a budget to purchase a moderately priced imaging system that operates at moderate speeds to upgrade the imaging system in the future with a module that configures the system to operate at faster speeds.
Other aspects of the present invention are directed to determining the number of exposing units on a module and configuring the imaging system to operate according to an imaging routine based upon the number of exposing units. For example, the removable module may include an on-board memory on which is stored data indicated of the number of exposing units. The imaging control circuitry may then access the module memory to determine the number of exposing units and then configured the imaging routine accordingly.
Alternatively, the removable module may be assigned a unique identifier, and the imaging system may be connected to a remote station, e.g., via the Internet. The remote station may include a database corresponding the unique identifier with the number of exposing units. Circuitry on the imaging system may then retrieve data from the database indicative of the number of exposing units based on the unique identifier.
Other aspects, features, and advantages of the present invention will become apparent as the invention becomes better understood by reading the following description in conjunction with the accompanying drawings.